Haplogroups are genetic populations that share a common ancestor, identified through specific DNA markers. They are often used in genetic genealogy to trace lineage and understand human migration patterns. Each haplogroup is designated by a letter and number, indicating its place in the human family tree. These groups can be determined through Y-DNA testing for males, which traces paternal lineage, or mtDNA testing for both genders, which traces maternal lineage. By studying haplogroups, researchers can gain insights into the ancestry of individuals and the historical movements of populations, such as those of Homo sapiens.